Gloves formed of elastomeric materials have been used in many applications: surgical gloves, examining gloves, food service gloves, and the like. Elastomeric materials have been found particularly suitable for such applications due to their physical characteristics. For example, elastomeric materials, in addition to having good elastic properties, exhibit good strength characteristics and may be produced so as to be impermeable not only to aqueous solutions, but also to many solvents and oils. Use of elastomeric gloves has provided an effective barrier between the wearer""s hand and the environment, successfully protecting both from cross-contamination.
Elastomeric gloves are typically formed so as to be stretched somewhat during normal use. For example, some gloves, especially examination and surgical gloves, are formed so as to be stretched during donning, in order to fit tightly against the hand and provide good gripping and tactile characteristics during use. In addition, the gloves should be impermeable to undesired substances, in order to provide a barrier between the wearer and the environment in which the gloves are used. Unfortunately, these desired characteristics of elastomeric gloves may create a harsh environment for the wearer""s skin. For example, perspiration is a common problem for glove wearers, and wearing gloves over a long period of time may be uncomfortable due to the trapped perspiration in the glove. In addition, the moist environment in the glove due to perspiration may exacerbate skin problems, including, for example, growth of fungi and yeast as well as bacterial and viral infections of the skin.
In the past, the skin contacting surface of the elastomeric articles were treated with a powder, such as talc or calcium carbonate powder to improve donning. The presence of the powders could also absorb some of the moisture and alleviate some of the problems the glove wearers faced. The use of powder was only partly successful, however, as there was a limited amount of moisture the powder could absorb. Additionally, in certain applications, such as clean-room type applications, powders could not be utilized at all.
What is needed in the art is an elastomeric glove which may provide the desired characteristics of either a powdered or a powder-free glove, while limiting or preventing the build-up of moisture between the hand and the glove during use. In other words, what is needed in the art is a breathable elastomeric glove.
Moisture Vapor Transmission Rate Test The following procedure is described for testing of the moisture vapor transmission rate (MVTR) for the breathable gloves of the invention. The MVTR is measured in a manner similar to ASTM Standard Test Method for Water Vapor Transmission of Materials, Designation E-96-80 as follows. For the purposes of the present invention, 3 inch diameter (76 mm) circular samples are cut from the test material and from a control material, CELGUARD.RTM. 2500 (Hoechst Celanese Corporation). CELGUARD.RTM. 2500 is a 0.0025 cm thick film composed of microporous polypropylene. Two or three samples are prepared for each material.
The cups used for testing are cast aluminum, flanged, 2 inches deep and come with a mechanical seal and neoprene gasket. The cups are distributed by Thwing-Albert Instrument Company, Philadelphia, Pa., under the designation Vapometer cup #681. One hundred millimeters of distilled water is poured into each Vapometer cup, and each of the individual samples of the test materials and control material are placed across the top area of an individual cup. Screw-on flanges are tightened to form a seal along the edges of the cups leaving the associated test material or control material exposed to the ambient atmosphere over a 62 millimeter diameter circular area (an open, exposed area of about 30 cm.sup.2). The cups are then weighed, placed on a tray, and set in a forced air oven set at 100xc2x0 F. (38xc2x0 C.).
The oven is a constant temperature oven with external air through it to prevent water vapor accumulation inside. A suitable forced air oven is, for example, a Blue M Power-O-Matic 60 oven distributed by Blue M Electric Co. of Blue Island, III. After 24 hours, the cups are removed from the oven and weighed. The preliminary test MVTR value is calculated as follows:
Test MVTR=[(grams weight loss over 24 hours)xc3x977571]÷24
The relative humidity within the oven is not specifically controlled. Under predetermined set conditions of 100xc2x0 F. and ambient relative humidity, the MVTR for CELGUARD.RTM. 2500 has been determined to be 5000 g/m2/24 hours. Accordingly, CELGUARD.RTM. 2500 is run as a control sample with each test and the resulting values are corrected in accord with the variation of the control relative to its known MVTR.
Mocon Water Vapor Transmission Rate Test
A suitable technique for determining the WVTR (water vapor transmission rate) value of a material is the test procedure standardized by INDA (Association of the Nonwoven Fabrics Industry), number IST-70.4-99, entitled xe2x80x9cSTANDARD TEST METHOD FOR WATER VAPOR TRANSMISSION RATE THROUGH NONWOVEN AND PLASTIC FILM USING A GUARD FILM AND VAPOR PRESSURE SENSORxe2x80x9d which is incorporated by reference herein. The INDA procedure provides for the determination of WVTR, the permeance of the film to water vapor and, for homogeneous materials, water vapor permeability coefficient.
The INDA test method is well known and will not be set forth in detail herein. However, the test procedure is summarized as follows. A dry chamber is separated from a wet chamber of known temperature and humidity by a permanent guard film and the sample material to be tested. The purpose of the guard film is to define a definite air gap and to quiet or still the air in the air gap while the air gap is characterized. The dry chamber, guard film, and the wet chamber make up a diffusion cell in which the test film is sealed. The sample holder is known as the Permatran-W model 100K manufactured by Mocon/Modern Controls, Inc. Minneapolis, Minn. A first test is made of the WVTR of the guard film and air gap between an evaporator assembly that generates 100 percent relative humidity. Water vapor diffuses through the air gap and the guard film and then mixes with a dry gas flow which is proportional to water vapor concentration. The electrical signal is routed to a computer for processing. The computer calculates the transmission rate of the air gap and guard film and stores the value for further use The transmission rate of the guard film and air gap is stored in the computer as CalC. The sample material is then sealed in the test cell. Again, water vapor diffuses through the air gap to the guard film and the test material and then mixes with a dry gas flow that sweeps the test material. Also, again, this mixture is carried to the vapor sensor. The computer then calculates the transmission rate of the combination of the air gap, the guard film, and the test material. This information is then used to calculate the transmission rate at which moisture is transmitted through the test material according to the equation:
TRxe2x88x921test material=TRxe2x88x921test material, guardfilm, airgapxe2x88x92TRxe2x88x921guardfilm, airgap
Calculations:
WVTR: The calculation of the WVTR uses the formula:
WVTR=Fxcfx81sat (T)RH/Axcfx81sat (T)(1xe2x88x92RH))
where:
F=The flow of water vapor in cc/min.,
xcfx81sat (T)=The density of water in saturated air at temperature T,
RH=The relative humidity at specified locations in the cell, A
A=The cross sectional area of the cell, and,
xcfx81sat (T)=The saturation vapor pressure of water vapor at temperature T
The present invention is generally directed to an elastomeric glove. More specifically, the glove of the present invention includes a substrate body made from at least one layer of a material and a breathability additive which is incorporated into the layer of the substrate body.
The material of the layer may be any material as is generally known in the art. For example, the material may be a material including one or more elastomeric block copolymers, hydrogel polymers, or polyurethane compositions.
The breathability additive incorporated into the layer of the substrate body may be polyethylene oxide. In one embodiment, the polyethylene oxide may be incorporated into the layer in an amount of between about 1 and about 70 parts per hundred by weight of the material. In one embodiment, the polyethylene oxide may be incorporated into the layer in an amount of between about 1 and about 30 parts per hundred by weight of the material.
The present invention is also directed to a process for forming breathable gloves. In general, the process includes providing a solvent, adding polyethylene oxide to the solvent to form a solution, adding the desired elastic material to the solution, forming a layer of the solution comprising the elastic material and the polyethylene oxide on a glove-shaped former, and drying the layer to form a glove on the former.